Inquiring Minds

Questions About Physics

Movement of the Electron Around the Nucleus

Question:
It is very enlightening to read your research and very
delightfull to explore our world.
Why does the electron have to move around the Nucleus? Why does it not
loose energy moving around it? If you say that they move in fixed energy
orbits why the electron still have to rotate? Lastly what decides the
energy orbits? Thanks so much.
-Arvind

Answer:
Dear Arvind,

You raise some really good questions:
Why does the electron have to move around the Nucleus? Why does it not
lose energy moving around it?

The answer is: although it is convenient to think of the electron moving
around the nucleus along circular paths, the correct description is a
quantum mechanical one. This is tough to visualize, and hence people have
stuck to the flawed picture of electrons moving along orbits. Incidentally,
the orbit picture (Bohr's model) gives the right answers for many physical
properties, including the energy needed for the electron to jump from one
energy (orbit) level to another one. This switch in energy (orbit) levels
occurs when the electron gains or loses energy through the absorption or
emission of a photon (which is a light particle with a certain amount of
energy, also called a quantum of energy).

In the more accurate quantum picture, the motion of the electron is
described by probability functions and there is no fixed orbit. Different
paths have different probabilities, and one can calculate average energy
levels. These energy levels turn out to have exactly the same values as the
energy levels calculated using the orbital (Bohr) model. However, the
probability picture avoids the problem of an orbiting object losing energy
through radiation.